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Tenth Anniversary Of The Darfield Earthquake - Expert Reaction
Ten years ago today, Cantabrians were woken by a major, unexpected shake.
The magnitude 7.1 quake was followed by a series of damaging aftershocks, including the fatal Christchurch earthquake six months later.
The SMC asked experts to comment on the progress made in earthquake science over the past decade.
Associate Professor Mark Quigley, School of Earth Sciences, University of Melbourne, comments:
"There have been more than 300 peer-reviewed research papers and several hundred reports published on the Darfield earthquake and associated Canterbury earthquake sequence in the decade since the 4 September 2010. This research spans the social and physical sciences, engineering, and the arts. It variably contributes to our communal understanding of hazard, vulnerability, exposure, and risk in the contexts of disaster response and recovery. It is authored from different perspectives, and with different objectives aimed at different audiences. It is challenging to distill these down to simple learnings from the 2010-2011 Canterbury earthquake sequence that could be described as ‘step-changes’ in national to international knowledge and practice, but there are a few things worth mentioning.
"The first is that the public clearly wanted to be taken on the scientific journey of discovery throughout this sequence, despite the complexities, uncertainties and adverse impacts embedded in many of our findings. For example, this was the first earthquake sequence in New Zealand in which earthquake forecasting was operationalised. This has carried forward and improved in recent earthquakes. The public responded well to public communications by scientists on science-in-progress, including backyard science. Landowners affected by zoning decisions often became aware of diverse types of relevant science through the local media, who reported well, and sought less traditional avenues for enabling scientific information to enter decision-making processes, such as contacting local scientists directly to request they provide advice in district plan hearings and court cases. Scientists built and sustained public trust despite the protracted and uncertain nature of this crisis; this reflects partly on their efforts, but also on the willingness of the general public to meaningful engage with science. I can assure you this is not globally ubiquitous.
"The second is that good governance comes in many forms and can be measured in many ways. From scientific, engineering, and economic perspectives, the NZ central government at the time, and many local leaders (such as those at the university and other key institutions) managed the Canterbury earthquake sequence very well, just as the current government has appropriately managed the COVID-19 crisis. Not every New Zealander will agree with me on this but that could reflect differences in how we might value different priorities as a society, and what the most important objectives are in responding to a crisis of this scale. The land use planning decisions (e.g., liquefaction and mass movement red zones) enacted in Christchurch were (mostly) evidence-based, drew heavily on scientific knowledge and advice, had adaptive capacity should new information come to light, and were precautionary in nature, with the intent to do the best by the collective society, even if local compromises had to be made.
"Central to good leadership through the Canterbury earthquake sequence was empowering individuals and teams with the autonomy to get the job done. In this science space, this was largely enabled through pre-existing funds provided by the Earthquake Commission that enabled us to respond quickly to acquire data and contribute efforts to rapidly emerging and changing scientific problems. Creating avenues for transparent and equitable allocations of rapid science funding at scale remains a major challenge in crises that can always be improved and that requires the efforts of many.
"The Darfield earthquake was one of the most complex earthquakes ever recorded at the time and remains so; it was associated with the sequenced rupture of at least 7 distinct faults. It really stimulated our thinking about how such fault systems behave and interact. We know now that that the last major earthquake on the Greendale Fault, prior to the Darfield earthquake, occurred around 22 to 28 thousand years prior to the Darfield earthquake and surface evidence for this event was buried by the outwash gravels of the Canterbury Plains. Similar fault systems reside throughout the Canterbury Plains and provide analogous sources of hazard. Our analyses suggest major rockfall events analogous to those experienced in the 2011 Christchurch earthquakes are expected to recur on the order of 3-5 thousand years. Liquefaction is expected to recur on the order of 100 – 300 years. These estimates do not preclude the occurrence of future events on significantly shorter timescales.
"Finally, tackling wicked multi-dimensional problems, such as response and recovery from a protracted earthquake sequence, requires the inclusion of diverse perspectives sourced from diverse individuals across industry, academia, and government. Much of the science that contributed most profoundly to our understanding of the Canterbury earthquake sequence, best shaped the trajectory of decision-making, and could be considered to be most influential, was sourced from diverse collaborations. Getting the balance right between institutions that often compete remains a challenge, but is an important endeavour, as evidenced from our experiences in the aftermath of the Darfield earthquake."
No conflict of interest.
Dr Tim Stahl, Senior Lecturer in Tectonics, School of Earth and Environment, University of Canterbury, comments:
"The September 4th Darfield earthquake ushered in a bittersweet decade in New Zealand earthquake geology. Geologists around the world have learned an immense amount from the Canterbury and Kaikōura earthquake sequences – and in many ways New Zealand scientists are now viewed as global leaders. With every new earthquake and aftershock (and yes, we still get them in Christchurch!) we are reminded that we cannot yet predict the specifics of when, where, and how big an event will be.
"However, our research into active faults around the country, into co-seismic hazards like landslides, and into how we best plan and prepare for disasters, have advanced immeasurably in the last decade. Part of this comes from having a community of excellent earthquake scientists and engineers with support from organisations like the New Zealand Earthquake Commission, which funds research into fundamental science questions that ultimately help reduce our vulnerability to earthquake hazards. We have a more resilient city and nation for having gone through the pain of the Canterbury earthquakes – all sparked by the rupture of an unknown fault under the Canterbury Plains that hadn’t previously moved for the last 30,000 years."
No conflict of interest.
Dr Bill Fry, Dr Caroline Holden and Dr Anna Kaiser, seismologists, GNS Science, comment:
"In the years leading up to the Darfield earthquake, GeoNet had the vision to support a regional earthquake monitoring network in the Canterbury Plains – an area that had been relatively quiet since monitoring began. When the Darfield earthquake happened right in the middle of the network, we had an up-close view of a large earthquake in New Zealand.
"The Darfield earthquake brought together a wide team of science experts from different disciplines. They were able to piece together a more complete picture of how the earthquake had unfolded and what could happen next. Models of the earthquake showed nine different faults had been involved – one of our first detailed studies of multi-fault rupture. Seismologists looked at the evolution of the rupture along the multiple faults and ground motion patterns. Earthquake geologists mapped the surface fault expression in detail to determine the extent and size of the primary Greendale Fault rupture. Geodesists used GPS and InSAR satellite data showing how the ground moved, to build models of the earthquake. Statistical seismologists looked at aftershock patterns and the probability of further events occurring in Canterbury. Social scientists were able to study ways to most effectively communicate information to the public and our wide end-user community. These studies were used to provide scientific advice to government ministers, first responders, local government, private enterprise, and of course the New Zealand public.
"The scientific advances made as a result of the Canterbury earthquake sequence served us well in the following decade of large earthquakes in New Zealand. Now, if an earthquake occurs, we are able to build detailed scientific models of the earthquake and its impacts in days to weeks instead of weeks to months. Through shared past response efforts, we have also forged strong connections within the scientific community and with our wide end-user community to better prepare for the future."
No conflict of interest.
Dr Jo Horrocks, Chief Resilience and Research Officer, EQC, comments:
Note: Jo's comments are excerpted from a longer piece which will be available on eqc.govt.nz.
"Little did we know on 4 September 2010, that the 7.1 Darfield earthquake was the announcement of a decade of the most destructive seismic activity that New Zealand has seen for more than 75 years.
"What we have also seen during this time, is New Zealand scientists and engineers responding to these earthquakes with innovations in techniques and advances in science, driven by a vision to reduce the harm to people and communities and wherever possible, reduce risk for the future.
"Although we now have a decade of science answers, being science, we also have a decade of new questions.
"One of the big questions thrown into prominence by the Kaikōura earthquake was what slow slip events – or “silent earthquakes”, where the tectonic forces are released over a much longer period of time – could mean for future major earthquakes. Advances in measurement using satellite technology linked to land survey data in GeoNet meant that scientists could see that the Kaikōura quake generated the most widespread triggering of slow-slip events following a crustal earthquake anywhere in the world. This poses important questions about how this relates to the Hikurangi subduction zone – one of our biggest natural hazards."
Conflict of interest statement: EQC has been a funder or part-funder of a number of earthquake science and engineering projects over the past decade.
Professor Paul Millar, College of Arts, University of Canterbury, comments:
"Our experience developing the CEISMIC Canterbury Earthquakes Digital Archive is that long-term research into the human dimensions of this major disaster was underfunded and treated as lower priority than infrastructure-focused projects. This is not a criticism of the need to build back better as rapidly as possible, but a call for recognition that traumatic events have a long tail. The impacts of a disaster like the Canterbury earthquakes remain a lived reality for people and communities for many years and deserve greater priority for research funding.
"It is only now, a decade after the first quake, that the CEISMIC archive is really coming into its own as a research resource for understanding the impacts of the quakes on people and communities. With greater support early, CEISMIC could have become even more substantial and useful as a transdisciplinary research tool. Early support for long-term and longitudinal studies by social scientists, educationalists, health researchers and the like has the potential to reveal much of value about ways to support and heal impacted communities.
"Our QuakeBox project—a longitudinal study of post-disaster narratives—has shown that even a decade after the Darfield event many people remain profoundly affected by their experiences. While most are trying to move on with their lives, their reactions to retelling their stories have ranged from therapeutic and cathartic through to traumatic, providing a worrying snap-shot of just how many Cantabrians still deal with post-disaster trauma."
Conflict of interest statement: Paul Millar received funding from the University of Canterbury and a variety of donors to develop the CEISMIC Canterbury Digital Archive. The QuakeBox project has been supported by a substantial grant from the RSNZ Marsden Fund.
Professor Alessandro Palermo, College of Engineering, University of Canterbury, comments:
"Ten years ago, the New Zealand structural engineering community received a strong wake-up call from Ruaumoko, the Māori god of earthquakes and volcanoes. The Darfield earthquake was a warning, while the 2011 February earthquake proved that there was a need for a design shift. But designing 'safe' bridges and buildings is not enough; society wanted and expected our built environment to be 'disruption free'. It is a similar scenario to what we are currently facing with COVID-19. Saving people's lives is a must, but we need to make our economies run too!
"In the last 10 years, engineers have had to learn to properly understand if a building/bridge can resist further earthquakes and researchers have tested similar details of buildings/bridges to support industry decisions. In the case of total replacement of damaged infrastructure, they had to come up with a better alternative since owners and insurers wanted buildings/bridges which are not only safe but also resilient such that business disruption is minimal. Some owners advertised this aspect (the resilience, disruption-free) while leasing their buildings.
"Since the early 2000s, the University of Canterbury was leading a front-edge research program on solutions for buildings and bridges, so-called low damage or disruption-free. Since the Canterbury earthquakes, researchers and engineers have worked more closely, and most of the groundbreaking research has been turned into a building or a bridge. The gap between research and industry has been closing in the last ten years. Several buildings adopt advanced dampers, or shock-absorbers, which are the product of recent researched. The Wigram Magdala Link Bridge in Christchurch is the first bridge in the world adopting a novel low-damage or disruption-free system developed by University of Canterbury researchers.
"The international earthquake engineering research community considers Christchurch the world 'capital' of built low-damage/disruption-free buildings and bridges. Does that mean it's game over? Unfortunately no, since the pathway to implementing those solutions is still complicated, and discourages engineers from using those "fancy" solutions. In the coming years, we researchers must support our engineers with the development of a straightforward regulatory process, so that solutions like the Wigram-Magdala bridge will become the new normal."
No conflict of interest.
Hanna Habibi, PhD student in Economics, Victoria University of Wellington, comments:
"In our recently-published paper, we show that the Canterbury earthquakes led to large improvements of earthquake preparedness in Canterbury and small improvements of preparedness in the rest of the country.
"The improvements in Canterbury reached their peak one month after the second earthquake and stayed positive 25 months later but declined by one third from its peak. This decline seemed to be the result of not keeping up with the short-lasting preparedness activities such as making an emergency plan or stocking water and food.
"The impact of the Canterbury earthquakes on improving short-lasting household preparedness in New Zealand appears to be fading out."
No conflict of interest declared.
Dr John Ristau, seismologist, GNS Science, comments:
"The M 7.1 Darfield earthquake had a major impact in New Zealand and how we respond to large earthquakes. The Darfield earthquake produced a surface rupture about 30 kilometres long on the previously unknown Greendale fault, and while this was the largest fault segment involved, it wasn’t the only one. The earthquake began on the (also unknown) Charing Cross Fault several kilometres to the north of the Greendale Fault, and the entire rupture involved at least six fault segments. Along with examples like the 2010 M 7.0 Haiti and M 7.8 Denali, Alaska earthquakes, it showed how major earthquakes are more complex than a single fault rupturing and has significant implications for seismic hazard assessment. The M 7.8 Kaikoura earthquake is the most extreme example of a major earthquake involving multiple fault ruptures.
"Ten years ago, GeoNet didn’t have the reputation it has today as New Zealand’s primary source of seismic information. In the first hours following the earthquake GeoNet gave the public the latest information on what had happened and the immediate impact of the earthquake, and in the days and weeks that followed, GeoNet and GNS Science provided information on aftershocks and what the people of Canterbury/Christchurch could expect to see as the sequence unfolded. We began to issue regular forecasts about the probabilities for large magnitude aftershocks and how long the aftershocks could be expected to last. GeoNet came to be seen a trusted source of seismic information for New Zealand, and this gave GeoNet the impetus to greatly expand the level of service it provides."
No conflict of interest.
Dr Natalie Balfour, GeoNet product development manager, GNS Science, comments:
"The Darfield earthquake marked the start of a new era for GeoNet: a shift in focus from providing data for research to speeding up our delivery of data and information to support geohazard event responses and recovery. Advances in our earthquake location system in the years following the Darfield earthquake enabled GeoNet to detect and locate earthquakes within minutes. The launch of the GeoNet mobile app enabled GeoNet to rapidly notify the public of earthquakes, and the development of Felt Rapid provided improved accessibility for the public to share their experiences of shaking through cartoon-based reports. Other improvements occurred through the density of the strong motion network in Canterbury and Wellington. These provided valuable insights into the intensity of shaking of large events following Darfield, such as 2012 Christchurch Earthquake, 2013 Cook Strait Sequences and 2016 Kaikoura Earthquake.
"Ten years on from this major earthquake, GNS Science now has a 24/7 operations centre that provides information on geohazards and support for earthquake, tsunami, volcano and landslide responses through monitoring data around the clock."
No conflict of interest.
Dr Elisabetta D’Anastasio, Geodetic Processing Specialist, GNS Science, comments:
"Measurements of ground deformation caused by large earthquakes provide an invaluable contribution to the understanding of large events. GeoNet operates a network of continuous GNSS (Global Navigation Satellite Systems) stations that are used to precisely determine the surface ground deformation on a daily basis. In the past 10 years, long term, permanent offsets caused by large events have been used in combination with seismological data, remote sensing (InSAR) measurements, and high rate GNSS measurements to model the earthquake source – and to precisely map surface deformation, fault slip at depth, and earthquake source parameters.
"Those studies are significantly contributing to seismic hazard modelling. We have learned the importance of combining traditional seismological techniques with precise geodetic measurements for large and strong regional events. In the past 10 years, thanks to the contribution of GNS scientists, we can build a good understanding of the earthquake source of significant events within a few days. Meanwhile, in partnership with Land Information New Zealand, some continuous GNSS stations have been upgraded to provide real time measurements sampled every second. In the next decade, we will focus on using these real time GNSS data (combined with other techniques such as InSAR) to improve our response to large events – from days to hours, or even minutes."
No conflict of interest.
Professor Mark Stirling, Chair of Earthquake Science, Department of Geology, University of Otago, comments:
"The M7.1 Darfield, Canterbury earthquake occurred 10 years ago, and was something of a wake-up call for seismologists. A number of lessons, or reminders, were gained from this earthquake, and it stimulated areas of research.
"We have been reminded that low seismicity regions away from tectonic plate boundaries can produce large earthquakes, but on a vastly longer time scale than the plate boundary regions. This results in considerable challenges for seismology. The areas are data-poor, in that earthquakes don’t occur very often, and earthquake recurrence statistics and resulting ground motions are very uncertain. Furthermore, the active faults that produce the major earthquakes in these regions often can't be seen on the ground surface due to the low rate of activity relative to other forces of nature (floods, erosion, deposition, vegetation cover, snow/ice cover). The Greendale Fault, source of the Darfield earthquake, produced its last earthquake between 20 and 30 thousand years ago, which predates the age of the Canterbury plains in the area of the earthquake.
"Some key seismological work can be directly attributed to the Darfield earthquake. This includes comprehensive reconstructions of the fault movement in 3 dimensions, and involving the use of multiple datasets; geology, geodesy, strong earthquake shaking, and InSAR. The Darfield event was a New Zealand first for such detailed reconstructions of a major earthquake in New Zealand.
"New ground motion models were also developed for New Zealand, ending a more than 10 year drought in model developments.
"We have recognised that there will be many unknown active faults in New Zealand, and an estimated 50% chance that our next major earthquake will be on an unknown fault of long recurrence interval/low activity. As a result, there has been effort placed on trying to model where these unknown faults might be, and the associated rates of activity. This has included the development of techniques for undertaking studies of ancient earthquakes in areas of low seismicity. Specifically, the first detailed studies of ancient liquefaction events in New Zealand were performed as a consequence of the Canterbury earthquake sequence.
"Seismic hazard models that change according to the natural decrease of aftershocks with time (so called time dependence) were developed for use in creating "building codes" for the rebuild of Christchurch. This had never been attempted anywhere in the world prior to Darfield.
"The Darfield quake created a stimulus to update the national seismic hazard model to incorporate time-dependence, new ground shaking models, and uncertainties in all the data and models at a national scale. The last model was completed just prior to the Darfield earthquake (I was leader of that model, along with the 1998 and 2002 models). The long process of acquiring funding has just come to a successful conclusion in the past month, with substantial financial support being gained for the national model update. The levels of funding are an order of magnitude bigger than those of the earlier national models, so the importance of updating national models has finally been realised in high places.
"Since Darfield, there has been much wider seismological community interest/involvement in seismic hazard modelling than the small groups I could muster for the earlier national seismic hazard models. These earlier models were developed by a smallish group of hazard researchers, with others mostly interested in pursuing their own core research areas. The core researchers also left it to the few of us to do the hard yards of translating their studies into practical hazard information. The Darfield earthquake and Canterbury earthquake sequence have resulted in much more proactivity in hazard modelling efforts from the wider seismological community."
No conflict of interest.
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